"Congratulations to my friend @harrisonjaime on officially launching his campaign to unseat Lindsey Graham in SC," Buttigieg, the mayor of South Bend, Ind., tweeted. "He will make a great Senator—and a positive change."

Congratulations to my friend @harrisonjaime on officially launching his campaign to unseat Lindsey Graham in SC. He will make a great Senator—and a positive change. https://t.co/zFD7m1FEjf